ABB Relion RES670, Applications Manual

Page: 204 / 382

7% 0, 07 x pu
= =
EQUATION1373 V1 EN-US
(Equation 85)
Equation 84 can be re-written in the following way without changing the value for
the operate time of the negative sequence inverse overcurrent IED:
2
2
1
op
NS
r
k
x
t
I
x I
×
=
æ ö
ç ÷
×
è ø
EQUATION1374 V1 EN-US
(Equation 86)
In order to achieve such protection functionality with one CVGAPC functions the
following must be done:
1. Connect three-phase generator currents to one CVGAPC instance (for
example, GF01)
2. Set parameter CurrentInput to value NegSeq
3. Set base current value to the rated generator current in primary amperes
4. Enable one overcurrent step (for example, OC1)
5. Select parameter
CurveType_OC1 to value Programmable
op
P
A
t k B
M C
æ ö
= × +
ç ÷
-
è ø
EQUATION1375 V1 EN-US
(Equation 87)
where:
t
op
is the operating time in seconds of the Inverse Time Overcurrent TOC/IDMT algorithm
k is time multiplier (parameter setting)
M is ratio between measured current magnitude and set pickup current level
A, B, C and P are user settable coefficients which determine the curve used for Inverse Time
Overcurrent TOC/IDMT calculation
When the equation 84 is compared with the equation 86 for the inverse time
characteristic of the OC1 it is obvious that if the following rules are followed:
1. set k equal to the generator negative sequence capability value
2. set
A_OC1 equal to the value 1/x2
3. set B_OC1 = 0.0, C_OC1 =0.0 and P_OC1 =2.0
4. set StartCurr_OC1 equal to the value x
then the OC1 step of the CVGAPC function can be used for generator negative
sequence inverse overcurrent protection.
Section 11
1MRK 511 407-UEN C
Multipurpose protection
198 Phasor measurement unit RES670 2.2 IEC
Application manual